It’s one of the funnier moments in the otherwise serious Mugen Train arc, but why does Inosuke give Nezuko acorns?
Inosuke chooses to give Nezuko acorns because she’s half-animal in his dream. She’s one of Inosuke’s “underlings,” and he offers her a shiny and smooth acorn if she’ll stand up and explore the cave with him.
Not much of Inosuke’s dream is shown, but Nezuko also shows up in Zenitsu and Tanjiro’s dreams as well.
Inosuke gives Nezuko acorns in a dream
In chapter #55, all the Demon Slayers upon the Mugen Train have fallen asleep. A demon, looking to destroy each Slayers’ spiritual core, has forced train workers to act underneath him. They punch each person’s ticket which puts them into a deep slumber.
Zenitsu’s dream-state involves a date with Nezuko. The two are running through a beautiful field of peaches, enjoying each other’s company and holding hands. Zenitsu offers to carry Nezuko on his back and jump over a body of water after she admits that she can’t swim.
We then see Inosuke’s dream. Cutting to the inside of a dark and dreary cavern, Inosuke shouts out “an expedition! We’re a team of cave explorers!” He’s still wearing his iconic boar mask.
Tanjiro and Zenitsu, dressed like cute animals, approach Inosuke and explain they sense the “lord of the cave” is somewhere up ahead. Nezuko, known by Inosuke as “underling 3,” is dressed as a rabbit.
In an effort to encourage Nezuko to stand up and work, Inosuke offers her a smooth and shiny acorn. She gladly stands up and the group sets off for adventure.
The extent to which Inosuke has this silly dream ends here. Far more time is given to Tanjiro’s dream, as it pushes the plot forward in a more meaningful and less comedic way.
So that’s the answer. Inosuke chooses to give Nezuko acorns because she’s part animal in his dream. Inosuke’s dream shows all the main characters as half-animal “underlings” who exist to serve him, and giving acorns to Nezuko is an effort to convince her to work.